A Voyage to the Inner-Most Planet

The Solar System has just become a little more known. This year our view of Mercury, the closest planet to the Sun, has changed as the Messenger spacecraft completes its first flyby of the little known world. Late in the afternoon last week, I braved the January cold to peer west. There, in the dusk twilight, was a single shining point below the crescent Moon.

Mercury usually shines at magnitude -1, and for millennia, that’s about all astronomers knew about the innermost planet. Speeding around the sun once every 88 days, the planet has always been too small and close to the sun for proper observation. Stories that Nicholas Copernicus never sighted the fleeting world are probably apocryphal. The planet is a difficult target, though not impossible! Until very recently, it was thought that Mercury kept one hemisphere “tidally locked” towards the sun. Through a telescope, Mercury shows a featureless sliver disk passing through distinct phases like the Moon and Venus. Mercury has also proved pivotal in science history; the mysterious precession of its perihelion was first attributed to a hidden inner planet named Vulcan (See “In Search of Planet Vulcan”):

http://astroguyz.com/?cat=11&paged=2

Later, it was shown that Einstein’s newly minted theory of relativity could adequately account for the anomaly; it still stands as one of the great proofs of relativity today.

Transits of Mercury can also prove to be inspiring. I viewed my first and only transit of Mercury from the grounds of the Flandreau Observatory in Tucson, Arizona on November 8th, 2006; no Vulcanoids were spotted. The next transit occurs on May 9th, 2016; a full list of transits can be viewed at;

Only one space probe has ever been sent to Mercury; in 1974-5, Mariner 10 performed a close flyby, imaging about a third of the sunlit surface. One of my favorite anecdotes of the mission was an account of a “moon” of Mercury that was briefly hypothesized. This was due to a spurious fluctuation of ultraviolet radiation, the source of which is still unknown. A cool account of this can be found here;

http://en.wikipedia.org/wiki/Mercury’s_moon

Very recently, astronomers using the SOAR (SOuthern Astrophysical Research) telescope managed to achieve unprecedented ground based images using a technique known as image stacking. (See Astroguyz “Imaging with an off the shelf web cam” ;

http://astroguyz.com/?cat=13

This enabled them to get images of awesome resolution.

Now comes Messenger to fill in the gaps. Already, its sent back some stunning, never before seen images. Messenger is scheduled for three fly-bys of Mercury before final orbital insertion on March 18th, 2011. While the first impressions reveal a world remarkably like the Moon, closer inspections show peculiarites. First, their is a total lack of maria, or flat plains, that dominate the lunar surface. Obviously, Mercury has undergone a severe bombardment early in its history. Secondly, its known to be the second densest object in the solar system, next to the Earth. This high “metallicity” rate has been suggested as a boon for carbon based life as we know it; we couldn’t have evolved in a hydrogen rich, heavy element poor environment. While I’m not suggesting that life on Mercury would be at all probable, (although an Arthur C. Clarke short story from “Islands in the Sky” suggests just that!) but it may guide our search for life farther a field. Interestingly, Mercury also pops in Kim Stanley Robinson’s “Blue Mars”… for a list of Mercury in fiction go to:

http://en.wikipedia.org/wiki/Mercury_in_fiction

But back to the science. Messenger will doubtlessly rewrite the story on Mercury, or at least render many of these old Sci-Fi tales obsolete. Messenger is armed with a science payload of six instruments. The list includes the Mercury Dual Imaging System, Gamma-Ray and Neutron Spectrometer, X-ray Spectrometer, Magnetometer, Laser Altimeter, and the Atmospheric and Composition Spectrometer. Messenger will bring an unmatched level of scrutiny to the tiny world. Look for additional updates on this site during subsequent flybys and eventual orbital insertion (yes, I do expect to be blogging that long!) Also, keep an eye out for the total lunar eclipse next month; I intend to do a two parter on measuring longitude via the Eclipse method next month! Messenger’s mission site can be found at:

Astro Documentaries

Pictured is a Delta IV rocket launch from Cape Canaveral on November 21st, 2010. The image is a 20 second exposure taken at dusk, shot from about 100 miles west of the launch site. The launch placed a classified payload in orbit for the United States Air Force.

DIY Astronomy

Difficult but not impossible to catch against the dawn or dusk sky, spotting an extreme crescent moon can be a challenge. The slender crescent pictured was shot 30 minutes before sunrise when the Moon was less than 20 hours away from New. A true feat of visual athletics to catch, a good pair of binoculars or a well aimed wide field telescopic view can help with the hunt.

The Sun is our nearest star, and goes through an 11-year cycle of activity. This image was taken via a properly filtered telescope, and shows the Sun as it appeared during its last maximum peak in 2003. This was during solar cycle #23, a period during which the Sun hurled several large flares Earthward. The next solar cycle is due to peak around 2013-14.

Astronomy Gear Reviews

Located in the belt of the constellation Orion, Messier 42, also known as the Orion Nebula is one of the finest deep sky objects in the northern hemisphere sky. Just visible as a faint smudge to the naked eye on a clear dark night, the Orion Nebula is a sure star party favorite, as it shows tendrils of gas contrasted with bright stars. M42 is a large stellar nursery, a star forming region about 1,000 light years distant.

Astronomical Observing Targets

Orbiting the planet in Low Earth Orbit (LEO) every 90 minutes, many people fail to realize that you can see the International Space Station (ISS) from most of the planet on a near-weekly basis. In fact, the ISS has been known to make up to four visible passes over the same location in one night. The image pictured is from the Fourth of July, 2011 and is a 20 second exposure of a bright ISS pass.

Next to the Sun, the two brightest objects in the sky are the Moon and the planet Venus. In fact, when Venus is favorably placed next to the Moon, it might just be possible to spot the two in the daytime. Another intriguing effect known as earthshine or ashen light is also seen in the image on the night side of the Moon; this is caused by sunlight reflected back off of the Earth towards our only satellite.

A mosaic of three images taken during the total lunar eclipse of December 21st, 2010. The eclipse occurred the same day as the winter solstice. The curve and size of the Earth’s shadow is apparent in the image.